Swollen shoot is a viral disease of cocoa that is developing in the region of Soubré and is causing very serious damage. However, little is known about the epidemiological factors responsible for this disease, which makes it difficult to control the swollen shoot virus. The main objective of this study was to determine the influence of plot maintenance level and the leaf cover of tree on the prevalence of Swollen shoot disease at the site of Petit-Bondoukou. The observation system consists of a sentinel size 10 km X 10 km. Each sentinel site is made up of 16 clusters of 2.5 km X 2.5 km containing about 10 plots which constitute the different observation points. In this study, observations were made in 4 plots of the site. The variables measured during data collection were the number of trees affected by the swollen shoot, the leaf cover level of each test tree and the maintenance level of sampling plots. A descriptive analysis was carried out with the data in order to understand their dispersal. Comparative analysis of swollen shoot prevalence and leaf cover level using the one-way ANOVA showed a significant relationship. Comparison of swollen shoot prevalence and plot maintenance level using the Kruskall-Wallis test showed that the prevalence of swollen shoot disease did not depend on the maintenance level. However, the leaf cover level of the test trees influenced the prevalence of swollen shoot disease. This is justified by the fact that test trees with low or medium leaf cover had significantly higher prevalences of CSSV.
Cassava is one of the main food crops in Africa, particularly in Côte d'Ivoire. However, the cultivated varieties are prone to attack by diseases. The present work focused on the role of phenolic and in particular flavonoid resistance markers in the Manihot esculenta-Colletotrichum gloeosporioides pathosystem. The aim was to elucidate the involvement of flavonoid antibiosis in the natural defense of three cultivars of M. esculenta when confronted with attacks by C. gloeosporioides. The quantitative dosage approach for total phenolics and flavonoids as well as the identification of flavonoid antibiosis have been carried out. The results revealed that the cultivars 9620A, TMS30572 and YACE of M. esculenta have, after the C. gloeosporioides inoculation tests, reacted early 2 days after inoculation (JAI) and accumulated relatively high levels of antibiosis phenolic and flavonoid 9JAI. The three cultivars accumulated constitutive flavonoid antibiosis and 3 neosynthesized antibiosis from 7JAI to 9JAI. The accumulation of flavonoid antibacterials neosynthesized in the stems and in the leaves testify to the expression of a systemic resistance of the cassava plants. The cultivars 9620A and TMS30572 are more tolerant than cultivar YACE. This study approach has made it possible to discriminate between cultivars and can therefore be used as a complementary selection tool to traditional selection tests.Keywords: Manihot esculenta, anthracnose, flavonoïd antibisis, glyphosate.
The high use of glyphosate for weed and pest control of cassava crops in Africa, particularly in Côte d'Ivoire, is correlated with the increasing extent of cassava anthracnose in the cassava producing regions. This health situation raises the question of the existence of a combined effect of glyphosate and anthracnose infection on the defence response of the cassava plant. The study was on the effect of glyphosate on antibiosis in M. esculenta in the pathosystem with C. gloeosporioides. To achieve this objective, a classical fully randomized 3-repeat device was used and antibiosis was the factor studied with 3 modalities. Treatments carried out on the plots, 4 months after planting, were inoculation of test plots of cassava with C. gloeosporoides before they were treated with 4JAI glyphosate. The assessment of phenolic and flavonoid antibiosis levels was carried out on leaf and stem organs harvested from 1JHA to 45 JHA and from the day of glyphosate treatment to 41 JHA. Comparative flavonoid antibiosis profiles were determined by CCM at the stages of maximum inhibition and maximum accumulation. Results showed that the phenolic and flavonoid antibiosis content of plants in glyphosate-treated plots decreased progressively in all varieties studied from JATr 1 to JATr 7. After the seventh day, the respective amounts of phenolic and flavonoid antibiosis gradually increased from the 8th JATr to the 180th JATr. This study showed a negative but partial interference of glyphosate in the defense mechanism of cassava cultivars (Manihot esculenta). Brou et al., 2021 Journal of Animal & Plant Sciences (J.Anim.Plant Sci. ISSN 2071-7024) Vol.48 (2): 8637-8648 https://doi.org/10.35759/JAnmPlSci.v48-2.1 8638 RESUME L’importante utilisation du glyphosate pour le désherbage et la lutte contre les adventices des cultures de manioc en Afrique et notamment en Côte d’Ivoire, et l’étendue croissante des cas d’anthracnose du manioc dans les régions de production de cette culture, soulève la question d’un possible effet conjugué du glyphosate et de l’infection à l’anthracnose. Les auteurs ont étudié l’effet du glyphosate sur les antibioses chez M. esculenta dans le pathosystème avec C. gloeosporioides. Pour atteindre cet objectif, un dispositif classique à trois répétions complètement randomisées a été utilisé et les antibioses sont le facteur étudié avec 3 modalités. Les traitements réalisés sur les parcelles, 4 mois après plant plantation, ont été l’inoculation des parcelles tests de manioc par C. gloeosporoides avant que celles-ci ne soient traitées par le glyphosate 4JAI. L’évaluation des teneurs en antibioses phénoliques et flavonoïdiques a été réalisée sur les organes feuilles et tiges récoltées de 1JAI à 45 JAI et du jour du traitement au glyphosate à 41 JAT. Les profils comparatifs en antibioses flavonoïdiques ont été déterminés par CCM aux stades de l’inhibition maximale et de l’accumulation maximale. Les résultats ont montré que la teneur en antibioses phénoliques et flavonoïdiques des plantes des parcelles traitées avec le glyphosate ont diminué progressivement chez toutes les variétés étudiées du 1er JATr au 7ème JATr. Après le septième jour, les quantités respectives des antibioses phénoliques et de flavonoïdes ont augmenté progressivement du 8ème JATr au 180ème JATr. Il ressort de cette étude, une interférence négative mais partielle du glyphosate dans le mécanisme de défense des cultivars de manioc (Manihot esculenta).
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